Stresses supported by thin films of Cu passivated by SiOx have been measured upon thermal cycling. Very high stresses have been found, approaching 1 GPa in the thinnest (40 nm) films. Strengthening beyond yield occurs upon both cooling and heating, indicative of strong strain hardening in the Cu. The hardening continues down to at least 77 K. The yielding behavior of the Cu films has been characterized by a kinematic constitutive law, with exceptional strain hardening and a conventional temperature-dependent yield strength. The physical basis for this behavior is ascribed to confined shear bands in the Cu that induce large back stress. Transmission electron microscopy reveals aligned dislocations, which seemingly dictate the inelastic deformations in the shear bands.

The characteristics of nanosized silicon nitride powders with doped Y2O3 and Al2O3 fabricated by a plasma-reacted chemical process were investigated. The chemical compositions of the powders were analyzed by wet chemical analysis. The morphology and the size distribution were determined by transmission electron microscopy (TEM). TEM with energy dispersive spectroscopy (EDS) was used to verify the existence of sintering additives in each individual particle. The crystal structure of the powders was identified by the selected area diffraction pattern (SADP). X-ray diffraction (XRD) technique was used for phase analysis and the measurement of degree of crystallinity. The characteristics of chemical bonding was analyzed by using Fourier transform infrared spectroscopy (FTIR).

Nanometer-size gadolinium powders (nm-Gd) have been prepared by means of evaporation condensation of Gd atoms within inert gas atmosphere. Microscopic analyses, based on measurements of small angle x-ray scattering (SAXS), x-ray diffraction (XRD), Raman scattering spectrum (RSS), and observation with transmission electron microscope (TEM), have been carried out in order to evaluate the size and size distribution of the as-prepared nm-Gd powder. It turns out that the size distribution function of nm-Gd powder agrees very well with the distribution function of Rayleigh instead of logarithmic distribution. The mean size d of nm-Gd powders bears a linear relationship with the logarithm of the pressure p of the inert gas atmosphere as follows: d = a + b · ln p. A discussion concerning the influence of particle size of nm-Gd powder on nanostructured material parameters such as the size distribution, specific surface area, and the percentage of interface atoms have been given in detail.

The effects of different growth parameters on the microstructure of the SiC films formed during simultaneous two-source molecular-beam-epitaxial (MBE) deposition have been investigated. Substrate temperatures as low as 750–900 °C have been used. The relationship between a number of different growth morphologies and deposition conditions has been established. The formation of single-crystal 3C films has been found to occur at low growth rates but within a limited Si: C adatom ratio. A combination of transmission electron microscopy (TEM) and atomic force microscopy (AFM) has been used to examine the different films, and the results of these investigations are described.

The thermal stability of TiSi2 films on Si has been studied using the atomic force microscope (AFM). Changes in the surface roughness, film morphology, and sheet resistance were monitored during a series of rapid thermal annealing treatments. A linear increase of the root-mean-square (rms) roughness with time was observed during the early stages of degradation, in agreement with a surface diffusion model of thermal grooving, followed by an apparent saturation roughness that was attributed to the effective rupture of the film.

Based on the experimental observation that high pressure will considerably enhance the crystallization onset temperature of amorphous alloys, an attempt was made to consolidate the melt-spun amorphous ribbons into fully densed three-dimensional bulk amorphous materials under high pressures. An amorphous Ni69Cr7Fe2.5Si8B13.5 (at. %) alloy was used as a model material. Under a pressure of 1.5 GPa, the crystallization onset temperature was found to be increased by about 40 K, resulting in a widened supercooled liquid temperature region (about 68 K) beneath the onset of crystallization. The high pressure consolidation of the amorphous ribbons in this temperature region yielded bulk amorphous compacts with the same density of the melt-spun ribbons. This achievement was attributed to the significant homogeneous viscous flow of materials in the supercooled liquid state that could be maintained at higher temperatures during the high pressure compaction.

Small titania particles, prepared by hydrolysis and condensation using in situ steric stabilization, have been studied by high-energy, transmission, electron energy-loss spectroscopy. Electron diffraction patterns and energy-loss spectra as a function of momentum transfer were measured for as-prepared particles (amorphous titania), particles annealed at 600 °C (primarily anatase), and particles annealed at 1000 °C (primarily rutile). The energy-loss spectra at low momentum disagreed with the loss function calculated from optical data (rutile) and disagreed with theory (rutile and anatase). The data was fit by an Elliot-like model for a resonant exciton interacting with a continuum of levels. The translational effective mass of the exciton derived from the fitting was quite large, indicating that it was self-trapped.

The low temperature pressureless sintering of a nanosized Si3N4 powder with doped sintering additives was investigated. The microstructural evolution during sintering at different temperatures was analyzed using x-ray diffraction and scanning electron microscopy. The effect of using nanosized Si3N4 powder as a catalyst to accelerate the α→β–Si3N4 transformation of a commercial Si3N4 powder with larger particle sizes was also investigated. Finally, two stage sintering was used to study the feasibility of controlling the microstructure and the mechanical properties of the nanosized silicon nitride.

Based on a thermodynamic assessment of the W–In–Ga–As quaternary system, the metal W was selected as a thermodynamically stable ohmic contact material to n-In0.53Ga0.47As. As-deposited contacts (on n ∼ 1.4 × 1018 cm−3 In0.53Ga0.47As) had average specific contact resistances of 7 × 10−7 Ω ·cm2 as measured using the transmission line model. The contact resistances remained unchanged after rapid thermal annealing at 400 °C for 1 min or at 600 °C for 1 min, and exhibited no degradation in electrical properties even after long-term annealing at 500 °C for 100 h. Transmission electron microscopic examination of the contacts showed no interfacial reaction. The present investigation demonstrates the power of thermodynamics in identifying stable ohmic contacts to multicomponent semiconductors.

A micromechanistic model of the combustion synthesis of NbC has been developed by combining the results of an experimental study of the intrinsic, pore-level kinetic mechanism [C. He. and G. C. Stangle, J. Mater. Res. 10, 2829–2841 (1995)] and a theoretical model developed previously [Y. Zhang and G. C. Stangle, J. Mater. Res. 9, 2592–2604 (1994); 9, 2605–2619 (1994)], in order to account for the various physical and chemical processes that take place during the combustion synthesis process. Results of the present investigation are interpreted from both a macroscopic and a microscopic point of view. Moreover, the relationship between the microscopic processes and macroscopic features of the combustion synthesis process is discussed. The results show that the formation of a combustion wave in the Nb-C system corresponded to establishment of a proper balance between the rates of enthalpy redistribution within the sample. Furthermore, the pore size had a significant influence on the combustion synthesis process: smaller pores gave rise to a higher area of contact between the reactants, which in turn gave rise to a higher rate of enthalpy increase due to the enhanced rate of product formation. The influence of the pore size distribution on the process is also discussed.

The effect of ternary addition on the thermal stability and the sequence and the kinetics of crystallization of metallic glasses Zr76Fe(24−x)Nix (x = 0, 4, 8, 12, 16, 20, 24) have been examined. It has been found that the surface crystallization occurs in the composition range 16 < x < 20, leading to the formation of an ordered Fe-rich (Fe, Ni)3Zr cubic phase, followed by the transformation of the bulk to a mixture of α−Zr and Zr2Ni. Crystallization of alloys containing 12 to 20% Fe occurs at lower temperatures by primary crystallization of Zr3(Fe, Ni), followed by decomposition of the remaining amorphous matrix by eutectic crystallization giving rise to α−Zr + Zr2Ni. At higher temperatures these alloys transform polymorphically to Zr3(Fe, Ni) in which Ni partially substitutes Fe in the Zr3Fe lattice. Copious nucleation of Zr3(Fe, Ni) phase in these alloys, leading to the formation of a nanophase structure, has been observed. This is consistent with the prediction of increasing nucleation rate for Fe-rich compositions. The crystal nucleation and growth kinetics have been examined for primary, eutectic, and polymorphic crystallization processes. The observed nucleation and growth behaviors have been rationalized by considering the role of the quenched in nuclei and the activation energies of nucleation and growth.

Due to the convective and radiant heat losses, there exists a maximal converted length of a dense pellet synthesized by the self-propagating high-temperature synthesis (SHS) method. In this paper, we numerically investigate the possibility to increase that maximal converted length by cascading two reactant pellets in series, where an interface is naturally and artificially introduced. First, the impacts of both the bulk and interfacial parameters on the SHS process are estimated. The maximal converted length for a single pellet is computed. Next, by varying the interfacial parameters, it is found that more than 10% of extra converted length is obtained by the proposed cascade arrangement. Effects of the bulk parameters on the same purpose are also addressed.

A detailed study has been made of the control and optimization of partial melting of dipcoated Bi2Sr2Ca1Cu2O8+δAg0.1 (Bi-2212) tapes using reduced oxygen partial pressures. A coulometric titration technique has been employed to vary the oxygen partial pressure in a region of the phase diagram corresponding to binary melting, and the amount of partial melting has been quantified. Using this information, tapes have been processed using both isothermal and isobaric techniques. An optimum processing route was determined which combined isothermal and isobaric processes. Highly aligned material at the point of optimum melting was obtained.

The oxidation behavior of a nanolayered MoSi2/SiC composite material was determined at the temperature range of 400–900 °C in wet oxidation conditions. The samples were produced in the form of thin films using a sputtering technique from two different sources, and a rotating substrate holder, onto silicon single crystals and low carbon steel. For comparison, the oxidations of both constituents, MoSi2 and SiC, produced with the same sputtering technique, were measured separately. The microstructure of the MoSi2/SiC samples was determined with high resolution transmission electron microscopy (HRTEM), and the composition of the sputtered samples was measured using backscattering (BS) of protons. For quantitative determination of oxidation, the nuclear reaction 16O(d, p)17O was utilized. Oxide layers were also analyzed using a secondary ion mass spectrometry (SIMS) and the appearance of the oxidized surface with a scanning electron microscopy (SEM). As expected, the SiC films had both the lowest initial oxidation and steady state oxidation rate. The results show that the oxidation behavior of the MoSi2/SiC nanolayered composite material differs from that of both its constituents and involves a degradation mechanism of its own, resulting in the highest oxidation during the initial phase of the oxidation. A steady-state oxidation rate was observed after the initial transient phase to be the highest for the metastable C40 structure of the single MoSi2 layer. The oxidation rate of the nanolayered structure was retarded by the SiC layers. No signs of pest disintegration were observed on either of the MoSi2 containing coatings during the steady-state phase of the oxidation at 500 °C up to 40 h. Our results show that the oxidation of nanolayered structures can be only in part explained by the oxidation behavior of the constituents and that during the steady-state oxidation of the nanolayered structure the oxidation rate is largely determined by the constituent with the lowest oxidation rate and by the layered structure.

The phenomena of pile-up and sink-in associated with nanoindentation have been found to have large effects on the measurements of the indentation modulus and hardness of copper. Pile-up (or sink-in) leads to contact areas that are greater than (or less than) the cross-sectional area of the indenter at a given depth. These effects lead to errors in the absolute measurement of mechanical properties by nanoindentation. To account for these effects, a new method of indenter tip shape calibration has been developed; it is based on measurements of contact compliance as well as direct SEM observations and measurements of the areas of large indentations. Application of this calibration technique to strain-hardened (pile-up) and annealed (sink-in) copper leads to a unique tip shape calibration for the diamond indenter itself, as well as to a material parameter, a, which characterizes the extent of pile-up or sink-in. Thus the shape of the indenter tip and nature of the material response are separated in this calibration method. Using this approach, it is possible to make accurate absolute measurements of hardness and indentation modulus by nanoindentation.

Polycrystalline RuO2 thin films were grown by metal-organic chemical vapor deposition (MOCVD) on both SiO2/Si(001) and Pt/Ti/SiO2/Si(001) substrates. Films having a controllable and reproducible structural texture and phase purity were synthesized by carefully controlling deposition parameters. Moderate growth temperatures (∼350 °C) and low growth rates (<30 Å/min) produced highly (110)-textured RuO2 films. Highly (101)-textured RuO2 films were favored at slightly lower temperatures (∼300 °C) and much higher growth rates (>30 Å/min). The most conductive RuO3 films had resistivities of 34 to 40 µΩ−cm at 25 °C, an average grain size of 65 ± 15 nm, and a surface roughness (rms) of 3 to 10 nm. Both single-phase Ru and mixed Ru/RuO2 phase material were also fabricated at low temperatures (<350 °C) by using lower oxygen flow concentrations (<10%).

High energy resolved x-ray emission spectroscopy with variable electron beam excitation is applied for study of solid-phase reactions in the Ir/(111)Si system as a function of annealing temperature. The formation of Ir silicides as a function of depth is studied by measurements of Si L2,3 x-ray emission valence spectra at different electron excitation energies (3–10 keV), and the results are compared with those of Rutherford backscattering.

High-temperature creep in undoped Al2O3 and La2O3- or Y2O3- or Lu2O3-doped Al2O3 with a grain size of about 1 µm is examined in uniaxial compression testing at temperatures between 1150 and 1350 °C. The high-temperature creep resistance in Al2O3 is highly improved by the rare-earth oxide doping in the level of 0.045 mol %, and the creep rate is suppressed in the order La2O3 <Y2O3 <Lu2O3. Rare-earth ions in each doped Al2O3 are found to segregate in Al2O3 grain boundaries without forming amorphous phase or second-phase particles. The activation energy for creep in undoped Al2O3 is estimated to be 410 kJ/mol, while it is about 800 kJ/mol in the three rare-earth oxide-doped Al2O3. The grain boundary diffusivity must be highly reduced by the segregation of the dopant cation in Al2O3 grain boundaries.

Nanometric maghemite and cobalt ferrite particles are chemically synthesized. The process produces particles polydisperse in size. The positive charges of their surface allow one to disperse them in aqueous acidic solutions and to obtain dispersions stabilized through electrostatic repulsions. Increasing acid concentration (in the range 0.1 to 0.5 mol.L−1), interparticles repulsions are screened and phase transitions are induced. Using this phenomenon, we describe a two-step size sorting process, in order to get significant amounts of nanometric monosized particles (with diameters monitored between typically 6 and 13 nm). As the surface of the latter is not modified by the size sorting process, usual procedures are used to disperse them in several aqueous or oily media.

In this study zinc sulfide thin films were grown by the successive ionic layer adsorption and reaction (SILAR) technique on (100) GaAs substrates from aqueous precursor solutions. The atomic force microscopy (AFM) method was used to study the growth of the films up to a thickness of 180 nm. The ZnS thin films on (100) GaAs were smooth with an rms roughness of 0.2–1.9 nm depending on the film thickness. After the GaAs surface was covered with ZnS, the growth appeared to be nearly layerwise. In addition, in situ AFM studies were carried out to analyze the dissolution of (100) GaAs in water, which is a process competing with the thin film deposition by the SILAR.